Quantitative ultrasound of the tibia: a novel approach for assessment of bone status.

An ultrasound instrument has recently been developed for the diagnosis and monitoring of osteoporosis (SoundScan 2000, Myriad Ultrasound Systems Ltd., Israel). The instrument measures the speed of propagation of ultrasound waves (SOS, meters per second) along a fixed longitudinal distance of the cortical layer at the tibial shaft. Its in vivo precision is 0.25%. The performance of the SoundScan 2000 was studied in 307 Caucasian women (age range 24-87 years) who also had their bone mineral density (BMD) measured at the spine, femoral neck, and radial shaft by absorptiometric techniques. The SOS ranged from 3471-4226 m/sec (mean 3867). The standardized coefficient of variation (CV), an expression of the effective clinical precision corrected for the spread of measurements (CV/[range/mean]), was 1.6% for the tibial SOS, compared to 1.5%, 3.8%, and 4.4% for spinal, femoral, and radial BMD, respectively. Tibial SOS significantly correlated with age (r = -0.52), time since menopause (r = -0.43), height (r = 0.29), and weight (r = 0.16), as well as with BMD at the radius (r = 0.63), spine (r = 0.50), and femur (r = 0.47). After classification of bone measurements into tertiles, about 60% of the women with low tertile spinal BMD fell within the low tertile of either tibial SOS, femoral BMD, or radial BMD. The results show that measurement of tibial SOS is a precise method of assessing bone status without exposing the patient to sources of radiation.